Arabidopsis E2Fc is required for the DNA damage response under UV‐B radiation epistatically over the microRNA396 and independently of E2Fe

Abstract

UV-B radiation inhibits plant growth, and this inhibition is, to a certain extent, regulated by miR396mediated repression of Growth Regulating Transcription factors (GRFs). Moreover, E2Fe transcription factor also modulates Arabidopsis leaf growth. Here, we provide evidence that, at UV-B intensities that induce DNA damage, E2Fc participates in the inhibition of cell proliferation. We demonstrate that E2Fc-deficient plants show a lower inhibition of leaf size under UV-B conditions that damage DNA, decreased cell death after exposure and altered SOG1 and ATR expression. Interestingly, the previously reported participation of E2Fe in UV-B responses, which is a transcriptional target of E2Fc, is independent and different from that described for E2Fc. Conversely, we here demonstrate that E2Fc has an epistatic role over the miR396 pathway under UV-B conditions. Finally, we show that inhibition of cell proliferation by UV-B is independent of the regulation of class II TCP transcription factors. Together, our results demonstrate that E2Fc is required for miR396 activity on cell proliferation under UV-B, and that its role is independent of E2Fe, probably modulating DNA damage responses through the regulation of SOG1 and ATR transcript levels.

The Plant DNA Damage Response: Signaling Pathways Leading to Growth Inhibition and Putative Role in Response to Stress Conditions

“…Interestingly, mutants deficient for histone acetyltransferases showed reduced growth inhibition after UV-B exposure, associated with altered expression of E2F transcription factors (Fina et al, 2017). Consistently, E2Fc know-down lines show less severe reduction of leaf growth in response to UV-B than the wild-type, suggesting that E2Fc could also play a role in the DDR activated by UV light (Gómez et al, 2019), as was previously suggested for the atypical E2Fe (Radziejwoski et al, 2011).…”

Connections between the Cell Cycle and the DNA Damage Response in Plants

“…In addition, and as already described in the animal field [113,114], the implication of these cell cycle regulators in DDR has clearly emerged [60]. As expected, a transcriptional control of DDR genes dependant notably on RBR1, E2FA, as well as E2FC, has been observed in Arabidopsis [62,110,111,115]. Also, RBR1 and E2FA have been shown to be recruited directly at the sites of DNA lesions, where they co-localise with γ-H2AX foci in an ATM-and ATR-dependent manner, suggesting their close participation in repair mechanisms [110,111,116].…”

The DREAM complex represses growth in response to DNA damage in Arabidopsis

“…In addition to the MuvB-core, we decided to also follow up the typical E2F transcription factors. Whereas E2FA ( Horvath et al, 2017 ) and E2FC ( Gómez et al, 2019 ) have previously been shown to be part of the DDR network, the role of E2FB has not yet been explored in detail. When we analyzed seedling roots expressing pgE2FA-3 x vYFP or pgE2FB-3 x vYFP by confocal microscopy after 24 h growth on cisplatin-containing or control plates, respectively, we observed that the overall E2FB signal seemed slightly enhanced after 24 h growth on genotoxin, whereas the E2FA signal was very similar to the signal in roots grown on control plates ( Fig 8A ).…”